Anhui Tiankang (Group) Co., Ltd.
When there are two different conductors or semi-conductors A and B that form a loop and the two ends are connected to each other, as long as the temperatures at the two junctions are different, the temperature at one end is T, which is called working end or hot end, and the other end is at temperature T0 Called the free end (also called the reference end) or the cold end, an electromotive force is generated in the loop. The direction and size of the electromotive force are related to the material of the conductor and the temperature of the two contacts. This phenomenon is called "thermoelectric effect", and the circuit composed of two conductors is called "thermocouple". These two kinds of conductors are called "hot electrodes" and the generated electromotive force is called "thermal electromotive force" [1].
The thermo-electromotive force consists of two parts of electromotive force, one is the contact electromotive force of the two conductors and the other is the thermoelectric emf of a single conductor.
The size of the thermoelectromotive force in the thermocouple circuit is only related to the temperature of the conductor material and the two contacts that make up the thermocouple, and is independent of the shape and size of the thermocouple. When the two electrode materials of the thermocouple are fixed, the thermo-electromotive force is the temperature t and t0 of the two junctions. The difference in function [1]. which is
This relationship has been widely used in actual temperature measurement. Because the cold end t0 is constant, the thermo-electromotive force generated by the thermocouple changes only with the change of the temperature of the hot end (measurement end), that is, a certain thermo-electromotive force corresponds to a certain temperature. We can achieve the purpose of temperature measurement by measuring the thermoelectromotive force [1].
The basic principle of thermocouple temperature measurement is that two different compositions of material conductors form a closed loop. When there is a temperature gradient at both ends, current will flow through the circuit. At this time, there is an electromotive force between the two ends—thermal EMF. This is the so-called Seebeck effect. The two different compositions of homogenous conductors are hot electrodes, with the higher temperature end being the working end, the lower temperature end being the free end, and the free end generally being at a constant temperature. According to the function relation of the thermo-electromotive force and the temperature, a thermocouple index table is made; the index table is obtained when the free end temperature is 0° C., and different thermocouples have different index tables.
When the third metal material is inserted in the thermocouple loop, the thermoelectric potential generated by the thermocouple will remain unchanged as long as the temperature of the two junctions of the material is the same, that is, it is not affected by the third metal in the loop. Therefore, when the thermocouple measures temperature, it can be connected to the measuring instrument. After the thermoelectromotive force is measured, the temperature of the measured medium can be known. When the thermocouple measures the temperature, the temperature of the cold end (the measuring end is the hot end and the end connected to the measuring circuit through the lead wire is called the cold end) remains unchanged, and the thermoelectric potential size has a certain proportional relationship with the measuring temperature. If the temperature of the cold end (ambient) changes during measurement, the accuracy of the measurement will be seriously affected. Take some measures at the cold end to compensate for the effects of changes in the cold junction temperature. The cold junction compensation known as a thermocouple is normal. Dedicated compensation wires for connection with measuring instruments.
Thermocouple cold junction compensation calculation method:
From millivolt to temperature: measure the cold junction temperature, convert to the corresponding millivolt value, and add the thermocouple's millivolt value to convert the temperature;
From temperature to millivolt: The actual temperature and the cold junction temperature are measured and converted to millivolts, respectively, and the millivolt value is subtracted to obtain the temperature.
The central motor we are referring to here is a central Ebike Motor used on lithium-ion assisted Electric Bicycles, while the common one is the motor used on lithium-ion mountain assisted bicycles. It was developed and put into use after the hub motor, and compared to the hub motor, the technology of the central motor is not yet very mature, so there is still a long way to go in terms of performance stability. But the central motor has a characteristic that hub motors do not have, which is its instantaneous starting assistance function, so it also has a corresponding market. The most common method is to install a center mounted motor on a mountain Electric Bike to meet the bumpy road conditions in the mountains, so both hub motors and center mounted motors have their advantages and disadvantages. The choice of motor depends entirely on which aspect of its functionality you value.Generally speaking, the central motor is used to assist mountain bikes, and hub motors are more common on urban series of assist bicycles.
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